1. Field of the Invention
The present invention relates to the general field of magnetic resonance imaging (MRI) and to apparatus improving MRI data acquisition and method for making and using same.
More particularly, the present invention relates to a resonating apparatus for use in magnetic resonance imaging or related fields including a plurality of closely packed, composite resonators and a plurality of lands, tags or tabs adapted to form decoupling capacitors between nearest neighbors and optionally also diagonal neighbors, when the resonators are in an array configuration and a pair of capacitive contacts adapted to connect each resonator to a monitoring device. The present inventions also relates to a fabrication process for making the resonator arrays of this invention where all external connections and all parts of necessary decoupling capacitors are built into the basic single resonator design becoming operable when the individual resonators are arranged in either in linear or planar arrays. The preferred design for each resonator in a given array configuration will vary depending on desired layout of the individual resonators.
2. Description of the Related Art
Since the inventions of magnetic resonance imaging (MRI) in 1973, significant advances and developments of this method has turned it into a widely used clinical and research tool, which provides an unsurpassed, non intrusive technique to image soft tissues. The MRI is related to the phenomenon of nuclear magnetic resonance (NMR), which is based on the excitation and relaxation of nuclei (most frequently protons) within living tissues in a DC magnetic field. An excitation repulse at the Larmor frequency v, which is the precession frequency of protons in DC magnetic field (ν=63.8 MHz for 1.5 Tesla), disturbs the equilibrium state of the nuclei. After the repulse, the nuclei relax to the equilibrium state with two different relaxation times (T1 and T2) and produce a weak decaying of signal.
In a MRI set-up, these weak decaying rf signals are detected by a receiver probe. For diagnostic usefulness of this signal, its level has to be well above the noise level, thus it puts premium on signal-to-noise ratio (SNR) of the receiver probe. In small volume MRI, MRI microscopy, low-field MRI, and NMR spectroscopy it has been shown that the Johnson noise of the rf receiver probe and/or preamplifier dominates, and thus determines the system noise floor.
In recent years, the design of phased arrays for parallel acquisition in MRI application has become the subject of a great deal of research. The drive for faster and faster acquisition rates calls for arrays with large number of receiving elements. As the number of array elements increases and their size continues to decrease, conductive losses become more dominant. These losses can overwhelm any signal-to-noise ratio (SNR) gains expected from the use of smaller coils that express less body noise.
Thus, it is desirable to reduce the thermal coil noise to improve the image resolution and reduce image acquisition time. Since the Johnson noise is a function of the product of resistance and temperature, reduction of either or both of these parameters enhances the SNR value of the MRI analysis. In addition, improved SNR can enable one to decrease voxel size and thereby increase the resolution of structural details.
Although many different MRI system exist, each has a limitation that involves the contribution of noise from the probe and the body being analyzed. As the need for greater resolution increases, the ability to use single coils is greatly reduced and the need for a different approach to signal acquisition is needed.
Thus, there is a need in the art for new probe structures that will operate in current and future MRI devices to increase signal acquisition with improved SNR and improved resolution without increasing the DC magnetic field strength or coil size.